Once sound has been converted to an electrical voltage, the “voltage image” can be amplified and then used to drive speakers. Like the skin of the bass drum, the movement of the speaker diaphragm compresses and decompresses air to produce sound. If the voltage is going upwards, the speaker will travel outwards; if the voltage is going downwards, the speaker will travel inwards. The resulting movement of the speaker will be parallel to the movement of the skin on the bass drum, to the movement of an eardrum, to the movement of the diaphragm within the microphone, and to the induced voltage.
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